Firefox and Thunderbird freeze system causing a reboot

Hi everyone,

I have a curious situation with my system since updating to 14.2-STABLE on
Tuesday, 5.11.'24: both Firefox and Thunderbird cause the system to freeze
which then triggers and automatic reboot. This doesn't happen immediately,
though. It takes at most 2:15 minutes until this freeze and reboot cycle
happens. No user-interaction is taking place during that time.

The machine is running FreeBSD 14.2-STABLE 
stable/14-n269500-cdffbea57c0d amd64.
Firefox is at version firefox-132.0.1_2,2 and Thunderbird at 
thunderbird-128.4.1_1.

Other gtk3-based programs do not show this behaviour, i.e., Inkscape,
Darktable, GIMP, EOG, Filezilla, Gnumeric.

I (re-)built both Firefox and Thunderbird with debugging symbols. Console
output of both Firefox and Thunderbird (when being started from an xterm)
can be found here:
philippost.de/firefox-debug-console-output
philippost.de/thunderbird-debug-console-output

In addition, I tried running them under truss(1), but from skimming through
both logs nothing immediately stood out at what could cause this.

Also, there's nothing to be found in the logs at all.

Did anyone else observed this? How do I go about debugging this?

I am at a loss at how to proceed and appreaciate any help in trying to
figure this out.

Best
Philipp